[PATCH v2] sunrpc: clean-up cache downcall

[Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx>]

We can simplify code around cache_downcall unifying memory
allocations using kvmalloc. This has the benefit of getting rid of
cache_slow_downcall (and queue_io_mutex), and also matches userland
allocation size and limits

Signed-off-by: Roberto Bergantinos Corpas <rbergant@xxxxxxxxxx>
---
 net/sunrpc/cache.c | 41 +++++++++++------------------------------
 1 file changed, 11 insertions(+), 30 deletions(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 20c93b68505e..1a2c1c44bb00 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -778,7 +778,6 @@ void cache_clean_deferred(void *owner)
  */
 
 static DEFINE_SPINLOCK(queue_lock);
-static DEFINE_MUTEX(queue_io_mutex);
 
 struct cache_queue {
 	struct list_head	list;
@@ -906,44 +905,26 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
 	return ret;
 }
 
-static ssize_t cache_slow_downcall(const char __user *buf,
-				   size_t count, struct cache_detail *cd)
-{
-	static char write_buf[32768]; /* protected by queue_io_mutex */
-	ssize_t ret = -EINVAL;
-
-	if (count >= sizeof(write_buf))
-		goto out;
-	mutex_lock(&queue_io_mutex);
-	ret = cache_do_downcall(write_buf, buf, count, cd);
-	mutex_unlock(&queue_io_mutex);
-out:
-	return ret;
-}
-
 static ssize_t cache_downcall(struct address_space *mapping,
 			      const char __user *buf,
 			      size_t count, struct cache_detail *cd)
 {
-	struct page *page;
-	char *kaddr;
+	char *write_buf;
 	ssize_t ret = -ENOMEM;
 
-	if (count >= PAGE_SIZE)
-		goto out_slow;
+	if (count >= 32768) { /* 32k is max userland buffer, lets check anyway */
+		ret = -EINVAL;
+		goto out;
+	}
 
-	page = find_or_create_page(mapping, 0, GFP_KERNEL);
-	if (!page)
-		goto out_slow;
+	write_buf = kvmalloc(count + 1, GFP_KERNEL);
+	if (!write_buf)
+		goto out;
 
-	kaddr = kmap(page);
-	ret = cache_do_downcall(kaddr, buf, count, cd);
-	kunmap(page);
-	unlock_page(page);
-	put_page(page);
+	ret = cache_do_downcall(write_buf, buf, count, cd);
+	kvfree(write_buf);
+out:
 	return ret;
-out_slow:
-	return cache_slow_downcall(buf, count, cd);
 }
 
 static ssize_t cache_write(struct file *filp, const char __user *buf,
-- 
2.21.0